1. Field of the Invention
The present invention relates to an electrical control system for adjusting the strength and speed of electrical drive motors of all types and phase wiring for any type of use and load. More particularly, the present invention relates to an electrical control system for a variable capacity compressor such as a scroll or rotary compressor wherein the eccentric of the compressor crankshaft is functionally connected to a unidirectionally operable orbiting scroll by a bearing or other type connector means or a reciprocating piston compressor typically used in single or multiple cylinder refrigeration, air conditioning systems or heat pumps or the like. It is contemplated that the control system of the present invention may also be used with a vacuum or other similar pumps or machines.
2. Description of the Related Art
Such variable capacity compressors are exemplified by the scroll compressor of U.S. Pat. No. 4,767,293, wherein the said connector means comprises the crankpin 126, the drive bushing 122, the bore 120, and the hub 118. Other compressors are exemplified by the wobble plate compressor of U.S. Pat. No. 5,129,792, the scotch yoke compressor of U.S. Pat. No. 4,838,769, and the reciprocating piston compressor of U.S. Pat. No. 5,238,370, the disclosures of all of which exemplary patents are hereby incorporated herein by reference in their entireties.
In all of such compressors it is often desirable to vary the compressor output, i.e., compressor capacity modulation, in accordance with cooling load requirements. Such modulation allows large gains in efficiency while normally providing reduced sound, improved reliability, and improved creature comforts including one or more of reduced air noise, better de-humidification, warmer air in heat pump mode, or the like.
Various approaches disclosed in the literature for achieving modulation in reciprocating piston compressors has been to switch the stroke length, i.e., stroke, by reversal of the motor and crankshaft rotation and the use of an eccentric bushing, of one or more of the reciprocating pistons whereby the volumetric capacity of the cylinder is changed. In these compressors the reciprocating motion of the piston is effected by the orbiting of a crankpin, i.e., crankshaft eccentric, which is attached to the piston by a connecting rod means of any of a variety of structures or configurations and which has a bearing in which the eccentric is rotatably mounted. Such switching devices are disclosed for example in U.S. Pat. Nos. 4,494,447; 4,236,874; 4,245,966; 4,479,419; and 4,248,053. It is apparent that such mechanical means would have no applicability to scroll compressors having the aforesaid unidirectionally operable scroll.